Method and apparatus for making a semiconductor device

ABSTRACT

Disclosed is an apparatus and method for yield enhancement of making a semiconductor device. The apparatus for yield enhancement of making a semiconductor device comprises: a semiconductor device comprising an epitaxial layer in which a defect is included, and a photo-resistor on the epitaxial layer and covering the defect; an image recognition system to detect and identify a location of the defect; and an exposing module comprising a first light source to expose a part of the photo-resistor substantially corresponding to the detected defect identified by the image recognition system.

TECHNICAL FIELD

The application relates to an apparatus and method for making asemiconductor device, and more particular to an apparatus and method foryield enhancement of making a semiconductor device by detecting a defectincluded in an epitaxial layer of the semiconductor device and forming aphoto-resist comprising a region substantially corresponding to thedetected defect.

DESCRIPTION OF BACKGROUND ART

Because the petroleum source is limited, various kinds of substitutiveenergy are developed extensively and turned into products. Among those,the solar cell has become the commercial products for either theindustrial or the residential use, and the III-V group material solarcell is mainly applied to the space industry and the industrial fieldbecause of its high conversion efficiency.

However, there are many kinds of defects existing in/on the epitaxiallayer of III-V group material. For example, as shown in FIG. 1, apinhole defect 101 which is usually caused by a dislocation under stressoccurs during the epitaxial growth of the III-V group material, andcracks 102 along the lattices also happen, especially in the waferbonding process or the substrate transferring process. There are otherkinds of defects, such as particles on the epitaxial layer or hilllockswhich are particles covered by the epitaxial layer and exists in theepitaxial layer. These defects in/on the epitaxial layer result indevice problems such as current leakage, and make the photovoltaicdevice operate abnormally. As the demand for a larger size photovoltaicdevice increases, the yield loss due to the defect becomes higher. Forexample, a 4-inch wafer produces only two photovoltaic devices used inaerospace industry, and the defect in/on the epitaxial layer results in50% yield loss accordingly. In some prior art, a laser is used to burnand remove the defects. However, it is difficult to remove the residualmaterial produced in the laser treatment, and the residual material mayalso lead to a current leakage.

SUMMARY OF THE DISCLOSURE

Disclosed is an apparatus and method for yield enhancement of making asemiconductor device. The apparatus for yield enhancement of making asemiconductor device comprises: a semiconductor device comprising anepitaxial layer in which a defect is included, and a photo-resist on theepitaxial layer and covering the defect; an image recognition system todetect and identify a location of the defect; and an exposing modulecomprising a first light source to expose a part of the photo-resistsubstantially corresponding to the detected defect identified by theimage recognition system. The method for yield enhancement of making asemiconductor device, comprises the steps of: providing a semiconductordevice comprising an epitaxial layer in which a defect is included;coating a photo-resist on the epitaxial layer; providing an imagerecognition system to detect and identify a location of the defect;exposing a part of the photo-resist substantially corresponding to thedetected defect identified by the image recognition system; developingto remove the exposed part of the photo-resist; and removing a part ofthe epitaxial layer where the photo-resist is removed. Also disclosed isa method for yield enhancement of making a semiconductor device,comprising the steps of providing a semiconductor device comprising anepitaxial layer in which a defect is included; providing an imagerecognition system to detect and identify a location of the defect;forming a photo-resist on the epitaxial layer, wherein a part of thephoto-resist is removed to substantially correspond to the detecteddefect identified by the image recognition system; and removing a partof the epitaxial layer with the photo-resist.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates defects existing in/on the epitaxial layer of III-Vgroup material of a photovoltaic device known in the prior art.

FIG. 2A illustrates the function block diagram of the apparatus inaccordance with one embodiment of the present application.

FIG. 2B illustrates the details of a part of the apparatus in FIG. 2A.

FIGS. 3A to 3L illustrate a method in accordance with one embodiment ofthe present application.

FIG. 4 illustrates the process of the exposing step related to themethod in FIGS. 3A to 3L.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 2A and FIG. 2B illustrate an apparatus in accordance with oneembodiment of the present application. FIG. 2A shows the function blockdiagram of the apparatus, and FIG. 2B illustrates the details of a partof the apparatus. Please refer to FIG. 2A. The apparatus 200 is used fordetecting a defect included in an epitaxial layer on a substrate of awafer and forming a photo-resist comprising a region substantiallycorresponding to the detected defect. The apparatus 200 comprises acoating module 210, an exposing module 220, a developing module 230, andan image recognition system 240. The apparatus 200 may further comprisea mask-used exposing module 250 to transfer a pattern on a mask, such ascutting lines, to the photo-resist for use in other process. It is notedthat the mask-used exposing “module” can also be in the form of an“apparatus” which is associated with the apparatus 200. Here a “module”means a part of an “apparatus” and provides a specific function in theapparatus when assembled to the apparatus. A module cannot functionindependently. In contrast, an apparatus can function independently, andcan be optionally associated with another apparatus to perform itsfunction. And “associated with” means the electrical signals areexchanged, and sometimes may also mean mechanical connection ifnecessary.

The coating module 210 is used to coat a photo-resist on the epitaxiallayer. The exposing module 220 comprising a first light source (notshown) is used to expose a part of the photo-resist. The imagerecognition system 240 is used to detect the defect and comprises asecond light source 241, an image sensor 242, and a comparison unit 243.It is noted that the image recognition system 240 can be set inside theexposing module 220 or a different module separated from the exposingmodule 220. In another embodiment, only some elements of the imagerecognition system 240 such as the second light source 241 and the imagesensor 242 are inside the exposing module 220, and the electricalsignals can be exchanged between the image recognition system 240 andthe exposing module 220. In the case that the whole image recognitionsystem 240 is set inside the exposing module 220 or in the case thatsome elements of the image recognition system 240 are set inside theexposing module 220, the defect detecting and the exposing step can beperformed substantially at the same time. That is, the defect isdetected by the image recognition system 240 and the part of thephoto-resist substantially corresponding to the defect detected isexposed by the exposing module 220 immediately. When the imagerecognition system 240 is not in a module separated from the exposingmodule 220, the time interval between the finish of defect detecting andthe actuation of the exposing step is very short because there is nottime spent on wafer transferring between two separated modules. If theimage recognition system 240 is set inside a module separated from theexposing module 220, the wafer may be first loaded into the module wherethe image recognition system 240 is set inside to detect the defect, andthen the information of the location of the defect detected is sent tothe exposing module 220 to which the wafer is then transferred, and thepart of the photo-resist substantially corresponding to the defectdetected is exposed accordingly.

As mentioned above, the apparatus 200 may further comprise a mask-usedexposing module 250 or be associated with a mask-used exposing apparatus250 to transfer a pattern on a mask to the photo-resist. A part of thephoto-resist corresponding to the pattern in the mask may be optionallyexposed by the mask-used exposing module (or apparatus) 250 before thedetecting step or after the exposing step. The part of the photo-resistcorresponding to the pattern in the mask together with the exposed partof the photo-resist substantially corresponding to the defect detectedmay be removed later in a developing step. The developing module 230 isused to develop the exposed photo-resist so the part of the photo-resistexposed by the first light source in the exposing module 220 and thepart exposed by the mask-used exposing module (or apparatus) 250 areremoved after the developing.

Please refer to FIG. 2B. The left part of the figure illustrates thedetails of the image recognition system 240 and some parts of theexposing module 220. The right part of the figure illustrates themask-used exposing module (or apparatus) 250. The image recognitionsystem 240 comprises elements enclosed by the broken line, i.e. thesecond light source 241, the image sensor 242, and the comparison unit243, and the exposing module 220 comprises a first light source 221 anda platform 222. As mentioned above, the figure shows the case which thewhole image recognition system 240 is set inside the exposing module 220and the electrical signals of the image recognition system 240 and theexposing module 220 are exchanged so that the detecting of the defectand the exposing step are performed substantially at the same time. Awafer 201 is loaded into the exposing module 220 and disposed on aplatform 222 of the exposing module 220. The platform 222 carries thewafer 201 and moves under the first light source 221 of the exposingmodule 220 and the second light source 241 and the image sensor 242 ofthe image recognition system 240. The second light source 241 providesillumination for image recognition and is different from the first lightsource 221 used for exposing. For example, when the photo-resist is apositive type photo-resist, the first light source is UV light whichcauses the positive type photo-resist to have a chemical reaction, andthe second light source is non-UV light which provides illumination forimage recognition and does not cause the positive type photo-resist tohave a chemical reaction. The image sensor 242 is used to capture animage of a pattern on the epitaxial layer on the wafer 201. The imagesensor 242 comprises, for example, a CCD (Charge-coupled Device) or aCMOS image sensor. The comparison unit 243 is used to compare the imageof the pattern captured by the image sensor 242 with a pre-determinedpattern stored in the comparison unit 243 for determining whether thepattern is a defect or not. The whole image recognition system 240 isset inside the exposing module 220 and the electrical signals of theimage recognition system 240 and associated with the exposing module 220are exchanged so that the detecting of the defect and the exposing stepare performed substantially at the same time. That is, the wafer 201 ismoved to be scanned by the image sensor 242, and when a defect isdetermined by the comparison unit 243, a signal from the comparison unit243 is transferred to the exposing module 220 so that the first lightsource 221 is actuated to expose the part of the photo-resistsubstantially corresponding to the defect detected.

In addition, as mentioned in FIG. 2A, the wafer 201 may be optionallytransferred to the mask-used exposing module (or apparatus) 250 beforethe detecting step or after the exposing step. It is noted that when thewafer 201 is transferred to the mask-used exposing module (or apparatus)250 before the detecting step, the wafer 201 is transferred directlyfrom the coating module 210 after the aforementioned coating step.

The mask-used exposing module (or apparatus) 250 comprises a mask table253 on which a mask 202 is disposed, a platform 252 on which the wafer201 is disposed on, and a light source 251. A part of the photo-resistcorresponding to a pattern in the mask 202 may be optionally exposed bythe mask-used exposing module (or apparatus) 250 with the light source251 before the detecting step or after the exposing step. The lightsource 251 may be the same as the first light source 221, i.e. UV light.The pattern in the mask 202 comprises, for example, cutting lines arounda solar cell chip.

FIGS. 3A to 3L illustrate a method in accordance with one embodiment ofthe present application. The method is used for removing a defect froman epitaxial layer on a substrate of a wafer and can be further used forforming a photovoltaic device. The method may be carried out with theutilization of the apparatus as previously illustrated in FIGS. 2A and2B.

As shown in FIG. 3A, the method comprises providing a wafer comprising asubstrate 301 on which an epitaxial stack 302 is formed first. Theepitaxial stack 302 comprises a plurality of layers of III-V groupmaterial to form at least one p-n junction of a solar cell. Theepitaxial stack 302 comprises a defect 302 d. The defect 302 d may beany one of those illustrated in FIG. 1. In FIG. 3B, a photo-resist 300 ris coated on the epitaxial stack 302 by the aforementioned coatingmodule 210. The wafer is then transferred to the aforementionedmask-used exposing module (or apparatus) 250 directly from the coatingmodule 210 after the coating step. As mentioned above, this embodimentillustrates a case which a mask-used exposing is performed before adefect detecting step. The defect detecting step will be illustratedlater in FIG. 3C. In the embodiment, a mask 300M is used, and thepattern in the mask 300M, which is a pattern for cutting lines 300MCaround a solar cell chip, is transferred to the photo-resist 300 r withan exposing by light (as the arrows shows) from the light source 251 ofthe mask-used exposing module (or apparatus) 250 shown in FIG. 2B. Theexposed pattern 300 rc in the photo-resist 300 r is used for forming thecutting lines in the wafer as will be illustrated later in FIG. 3E.

As shown in FIG. 3C, this embodiment illustrates a case which thedetecting of the defect and an exposing step are performed substantiallyat the same time by using the apparatus shown in FIG. 2B, and the waferis transferred to the aforementioned exposing module 220 and a defectdetecting step is performed. The wafer is scanned by the aforementionedimage sensor 242 with the illumination provided by light from the secondlight source 241. And once a defect, for example, the defect 302 d isdetected, the first light source 221 is actuated to expose the part ofthe photo-resist 300 rd which is substantially corresponding to thedefect detected. The first light source 221 used for exposing isdifferent from the second light source 241 for image recognition. Forexample, the photo-resist 300 r in this embodiment is a positive typephoto-resist, and the first light source 221 is UV light which causesthe positive type photo-resist 300 r to have a chemical reaction, andthe second light source 241 is non-UV light which provides illuminationfor image recognition and does not cause the positive type photo-resistto have a chemical reaction. The process of the exposing step isillustrated in FIG. 4. In FIG. 4, the light from the first light source221 is projected onto the defect and forms a spot as denoted as acircle. The wafer is moved as the aforementioned platform 222 carryingthe wafer moves, and spots are formed upon the wafer. In this example,as mentioned previously in FIG. 1, two kinds of defects, i.e., a pinholedefect 101 and cracks 102 are shown, and the area of these defects formsa defect area. The spots as denoted are formed substantially along thecontour of the defect area and cover the whole defect area. Finally, thecollection of these circles forms the exposed part as denoted by thesolid line in the figure to cover the defect area. The area of theexposed part is substantial the same as or a little larger than thedefect area. It is noted that the information of the location of thedefect detected may be stored in the same apparatus or sent to anotherapparatus for a later use.

And then as shown in FIG. 3D, the wafer is transferred to theaforementioned developing module 230, and the photo-resist 300 r isdeveloped to remove the exposed part of the photo-resist 300 r so that asubsequent etch process is performed with the developed photo-resist 300r as a mask to remove the part of the epitaxial layer where thephoto-resist is removed. The result after the etch process is shown inFIG. 3E where an empty part 302 d′ substantially corresponding to thedefect 302 d detected and an empty part 302 c corresponding to a cuttingline are formed in the epitaxial stack. The etch process may be a dryetch or a wet etch, and the photo-resist 300 r is removed after the etchprocess. Then as shown in FIGS. 3F to 3J, a dielectric material isformed substantially in the region where the epitaxial stack 302 isremoved; in other words, a dielectric material is formed in the emptypart 302 d′ and the empty part 302 c shown in FIG. 3E. As shown in FIG.3F, a dielectric layer 303 is formed. The dielectric layer 303 may be,for example, alumina, titanium dioxide, silicon nitride (SiN_(x)) orsilicon oxide (SiO_(x)). In FIG. 3G, a negative photo-resist 300R iscoated on the dielectric layer 303, and an exposing is performed on thephoto-resist 300R with a mask 300M2. The area of the pattern 300M2C maybe a little larger than the area of the pattern 300MC in FIG. 3B. Theexposing can be performed by the mask-used exposing module (orapparatus) 250. Since the photo-resist 300R is a negative type, as willbe illustrated in FIG. 3I, the exposed part is left as a remaining partafter developing. And then in FIG. 3H, the information of the locationof the defect detected stored as previously mentioned in FIG. 3C is usedso that an exposing step may be carried out accordingly. The area of theexposed part can be substantial the same as or a little larger than thearea of the empty part 302 d′ shown in FIG. 3E. As a result, as shown inFIG. 3I, after a developing step, a first remaining part 300RDsubstantially corresponding to the area of the defect 302 d detected anda second remaining part 300RC corresponding to cutting lines of thenegative photo-resist 300R are formed on the dielectric layer 303. Andthen in FIG. 3J, an etch process is performed to remove the part of thedielectric layer 303 uncovered by the first remaining part 300RD and thesecond remaining part 300RC of the photo-resist 300R, and dielectricmaterial 303D and 303C is formed substantially in the region where theepitaxial layer is removed. The etch process may be a dry etch or a wetetch, and first and second remaining parts 300RD and 300RC of thephoto-resist are removed after the etch process. The dielectric material303D is formed in the region corresponding to the empty part 302 d′ inFIG. 3E which is removed for the defect 302 d, and the dielectricmaterial 303C is formed in the region corresponding to empty part 302 cin FIG. 3E which is removed for the cutting lines 303 c. The dielectricmaterial 303D provides an electrical isolation to the sidewalls of theempty part 302 d′, and therefore avoids forming a current leakage pathor the failure of the p-n junction in the epitaxial stack 302. Inaddition, when an electrode passes or is located on the empty part 302d′, the dielectric material 303D provides an electrical isolationbetween the electrode and the junction to avoids a shortage.

As shown in FIG. 3K, an anti-reflective layer 304, the first electrode305, and the second electrode 306 are subsequently formed. The mainportion of the anti-reflective layer 304 is formed on the epitaxialstack 302 while a portion of the anti-reflective layer 304 is formed onthe dielectric material 303D to fill the concave part caused by theempty part 302 d′ in FIG. 3E with the dielectric material 303D formedthereon. The first electrode 305 is formed in the anti-reflective layer304 and on the epitaxial stack 302. The second electrode 306 is formedon the surface of substrate 301 opposite to the surface on which theepitaxial stack 302 is disposed. And in FIG. 3L, as mentioned above, thecutting lines are formed around a solar cell chip, and the substrate 301is cut along the cutting lines as indicated by the line LL′ to form thesolar cell chips.

It is noted that the process flow shown in this embodiment may beadjusted by the person of the skill in the art. For example, though thecutting line pattern, i.e. the mask-used exposing, is performed beforethe detecting step in this embodiment, it is apparent that the mask-usedexposing may be performed after the detecting step. Besides, the coatingstep may be performed after the detecting step. For example, the wafermay be first loaded to an separated module where the image recognitionsystem 240 is set inside (or the exposing module 220 comprising an imagerecognition system set inside it) to have the detecting step performed,and then the wafer is transferred to the coating module 210 to have thecoating step performed. And finally the stored information of thelocation of the detected defect is used in the exposing module 220 tohave the exposing step performed accordingly after the coating step.Similarly, the order for the wafer to be transferred between differentmodules in the apparatus may be designed by the person of the skill inthe art accordingly as the above illustration. In addition, though thefour modules are integrated in one apparatus as shown in FIG. 2A, one ormore modules may be separated and formed as an independent apparatus bythe person of the skill in the art. It is also noted that application ofthe apparatus and the method illustrated in the present application isnot limited to a photovoltaic device, and can be commonly used for asemiconductor device, such as an LED. The yield of the semiconductordevice is enhanced by detecting and removing the defect included in anepitaxial layer of the semiconductor device and forming a dielectricmaterial in the region where the epitaxial layer is removed to providean electrical isolation and avoid problems such as current leakage.

The above-mentioned embodiments are only examples to illustrate theprinciple of the present invention and its effect, rather than be usedto limit the present invention. Other alternatives and modifications maybe made by a person of ordinary skill in the art of the presentapplication without escaping the spirit and scope of the application,and are within the scope of the present application.

What is claimed is:
 1. A method for yield enhancement of making asemiconductor device, comprising the steps of: providing a semiconductordevice comprising an epitaxial layer in which a defect is included;coating a photo-resist on the epitaxial layer; detecting and identifyinga location of the defect by an image recognition system; exposing a partof the photo-resist substantially corresponding to the detected defectidentified by the image recognition system; developing to remove theexposed part of the photo-resist; removing a part of the epitaxial layerwhere the photo-resist is removed; and forming a dielectric materialsubstantially in a region where the epitaxial layer is removed, whereinsaid removing the part of the epitaxial layer comprises an etchingprocess.
 2. The method as claimed in claim 1, wherein the coating stepis performed after the detecting step.
 3. The method as claimed in claim1, wherein the detecting step and the exposing step are performedsubstantially at the same time.
 4. A method for yield enhancement ofmaking a semiconductor device, comprising the steps of: providing asemiconductor device comprising an epitaxial layer in which a defect isincluded; detecting and identifying a location of the defect by an imagerecognition system; forming a photo-resist on the epitaxial layer,wherein a part of the photo-resist is removed to substantiallycorrespond to the detected defect identified by the image recognitionsystem; removing a part of the epitaxial layer with the photo-resist;and removing the photo-resist and forming a dielectric material in aregion substantially corresponding to the part which the epitaxial layeris removed, wherein said removing the part of the epitaxial layercomprises an etching process.
 5. The method as claimed in claim 4,further comprising forming an anti-reflective layer on the epitaxiallayer and the dielectric material.
 6. The method as claimed in claim 5,further comprising forming an electrode disposed in the anti-reflectivelayer and on the epitaxial layer.
 7. The method as claimed in claim 1,further comprising providing a mask and exposing the photo-resist withthe mask to expose a cutting line pattern on the photo-resist before thedetecting step or after the exposing step, and the part of thephoto-resist for the cutting line pattern is removed in the developingstep.